Maine To Release Parasitic Flies To Stop Tree-killing Moths

May 7, 2018

The Maine Forest Service plans to release parasitic flies in South Portland later this week to help control the pesky winter moth population.

The invasive species kills oaks and other leafy trees and shrubs. Maine Forest Service Entomologist Colleen Teerling says cages containing fly cocoons were buried in the woods in South Portland last November to overwinter and are now emerging as adults.

The flies are expected to lay eggs on oak leaves.

“The winter moth will eat the leaves containing the eggs and the eggs will then hatch in the gut of the winter moth,” Teerling says.

She says South Portland is the fifth coastal Maine location where flies have been released. She says it may take five or ten years for winter moth numbers to come down.

“Which sounds like a long time but in terms of biological control that’s incredibly fast,” Teerling says. “Some biological control programs, especially in the forest, can take a century before you actually see the numbers come down.”

Portland Press Herald reports Monday that two South Portland groups have canceled their plant sale this year, out of fear sales might continue the spread of winter moths.